CN111193447B - A torque ripple suppression method for open-winding permanent magnet synchronous motor - Google Patents

Abstract

The invention provides a torque pulsation suppression method of an open-winding permanent magnet synchronous motor. By analyzing the torque components of the open-winding permanent magnet synchronous motor, and using the q-axis current reverse injection method, the method can be used in various complex working conditions. It can effectively suppress the zero-sequence torque ripple and improve the working efficiency and running stability of the motor. The method is based on ESO's zero-sequence loop model-free idea, which gets _rid of the drawback of high dependence on zero-sequence loop parameters in the calculation process. Control effect. The ESO control principle adopted in the method is simple and requires less computation.

Description

A torque ripple suppression method for open-winding permanent magnet synchronous motor

technical field

The invention relates to the field of torque pulsation suppression in the control of an open-winding permanent magnet synchronous motor, in particular to a suppression technology for torque pulsation generated by a zero-sequence loop.

Background technique

The open-winding permanent magnet synchronous motor powered by a single power supply has the advantage of saving space, so it is widely used. However, due to its inherent zero-sequence loop, the zero-sequence current in it will generate zero-sequence torque ripple, which will adversely affect the running stability of the motor, thereby reducing the efficiency of the motor. Therefore, it is necessary to effectively suppress the zero-sequence torque ripple. The torque ripple generated by the zero-sequence current can be realized by suppressing the zero-sequence current, but the zero-voltage vector redistribution strategy widely used at this stage cannot guarantee that the zero-sequence current can always get a good suppression effect under complex working conditions. Wei Hu et al. proposed a scheme to suppress the zero-sequence torque ripple using the q-axis current reverse injection method in the paper "Torque Ripple Suppression Method With Reduced SwitchingFrequency for Open-Winding PMSM Drives With Common DC Bus", but the article does not There is no mention of cases where the zero-order parameter is inaccurate. In "Torque Ripple Suppression for Open-end Winding Permanent-Magnet Synchronous Machine Drives with Predictive Current Control", Yuan Xin et al. proposed a method of calculating the reverse injection q-axis reference current value by using a synovial variable structure method, but the The used synovial membrane structure is relatively complex and requires a large amount of calculation, and the zero-sequence current cannot be effectively suppressed by the central hexagonal modulation technology. Therefore, there is an urgent need in the art for a control strategy that can effectively suppress the zero-sequence torque ripple generated by the zero-sequence current without putting too much pressure on the control system.

SUMMARY OF THE INVENTION

In order to solve the shortcomings of the existing torque ripple suppression strategies, especially for the obvious zero-sequence torque ripple generated when the zero-sequence parameters change during the operation of the motor, and the deterioration of the motor running stability, this paper The invention provides a torque ripple suppression method for an open-winding permanent magnet synchronous motor, which specifically includes the following steps:

Step 1: Collect the three-phase stator current, motor speed, and rotor position angle of the open-winding permanent magnet synchronous motor at the current moment in real time, and convert each parameter into the form in the quadrature-axis d-q coordinate system;

Step 2: Establish a mathematical model for the permanent magnet synchronous motor in the d-q coordinate system, and use the deadbeat current predictive control model to predict the quadrature axis and the straight axis at the next moment in combination with the current moment parameters collected in step 1. and use the extended observer (ESO) to perform model-free control in the zero-sequence loop of the model to predict the zero-sequence current and zero-sequence back EMF at the next moment;

Step 3: Using the zero-sequence current and zero-sequence back EMF predicted in step 2, calculate the required reverse injection value of quadrature current;

Step 4: Based on the calculation results in Steps 2 and 3, output the required voltage after the torque ripple is suppressed, and perform SVPWM modulation.

Further, in the step 2, establishing a mathematical model for the permanent magnet synchronous motor under the d-q coordinate system is specifically:

In the formula, U _d , U _q , and U ₀ are the direct axis, quadrature axis and zero-sequence voltage of the motor in the _dq coordinate system, respectively; id , i _q , and i ₀ are the direct axis, quadrature axis, and zero-sequence current, respectively; Ψ _f is Motor rotor permanent magnet flux linkage; R _s is stator resistance; L _d , L _q , L ₀ are d-axis, q-axis and zero-sequence inductance respectively; ω _r is the electrical angular velocity of the rotor, e ₀ is zero-sequence back EMF, t is time; in the surface-mounted open-winding permanent magnet synchronous motor used, L _d =L _q =L _s . Discretize the above model.

Further, in the second step, the deadbeat current predictive control model is used to predict the quadrature axis and the direct axis current at the next moment, based on the following formula:

分别为下一时刻的交轴、直轴电流预测值，T_k为一个控制周期。In the formula, k represents the current moment, k+1 is the next moment,

are the predicted values of the quadrature-axis and direct-axis currents at the next moment, respectively, and _Tk is a control cycle.

In the zero-sequence loop of the model, an extended observer (ESO) is used to perform model-free control, and the zero-sequence current and zero-sequence back EMF at the next moment are predicted, including:

Since the target current of the zero-sequence current i ₀ is 0 when the open-winding permanent magnet synchronous motor is in normal operation, when the motor speed is not too high, when the modulation technique of zero voltage vector redistribution is adopted, i ₀ will be close to 0, At the same time, the value of R _s i ₀ is very small compared to e ₀ , so the zero-sequence loop can be regarded as having the following relationship:

Model-free control with extended observers is based on the following relation:

where α is a parameter selected according to the motor controller, set here as L ₀ , F is a comprehensive representation of the known part and the unknown part, F=R _S i ₀ +e ₀ , using the modulation of zero-voltage vector redistribution At the same time, the value of R _s i ₀ is very small compared to e ₀ , so F≈e _{0 ; the initial value of e 0 is} usually set to 0. Therefore, the zero-sequence current and zero-sequence back EMF at the next moment can be predicted based on the following formula:

与零序电流实际值i₀(k)之间的误差，T_k为系统一个离散周期，

也即

为零序反电势估计值，β₁与β₂为扩张观测器参数。Among them, er ₀ represents the predicted value of zero-sequence current at time k

The error between the actual value of the zero-sequence current i ₀ (k), T _k is a discrete period of the system,

that is

Estimated value of zero-sequence back EMF, β ₁ and β ₂ are extended observer parameters.

Further, the calculation of the reverse injection value of the quadrature axis current in the step 3 specifically includes:

Since the surface-mounted open-winding permanent magnet synchronous motor torque T _e is expressed as follows:

where p is the number of motor pole pairs. It can be seen that the torque of the open-winding permanent magnet synchronous motor consists of two parts: the torque generated by the quadrature axis current and the torque generated by the zero sequence current. In order to effectively suppress the torque generated by the zero-sequence current, the required reverse injection reference current value i' _q for the quadrature axis is:

Substitute the zero-sequence current and the zero-sequence back EMF predicted in step 2 to obtain the reverse injection value of the quadrature-axis current.

Further, the required voltage after the output torque ripple is suppressed in the step 4 is specifically:

分别为k时刻的各实际参考电流。in,

are the actual reference currents at time k, respectively.

Through the method provided by the present invention, at least the following beneficial effects can be achieved:

1. The above method analyzes the torque components of the open-winding permanent magnet synchronous motor, and adopts the q-axis current reverse injection method, which can effectively suppress the zero-sequence torque ripple under various complex working conditions and improve the motor's performance. Work efficiency and running stability;

2. The above method adopts the idea of zero-sequence loop model-free based on ESO, which gets rid of the drawback of high dependence on zero-sequence loop parameters in the calculation process. When the motor zero-sequence parameters (especially the third flux linkage Ψ _3f ) change , still has a good control effect.

3. The ESO control principle adopted in the method is simple and the amount of calculation is small.

Description of drawings

Fig. 1 is the flow chart of the method provided by the present invention;

Fig. 2 is based on the principle diagram that the method provided by the present invention splits the winding permanent magnet synchronous motor control;

Fig. 3 is the torque ripple diagram without adopting the method provided by the present invention under the condition that the tertiary flux linkage does not change;

Fig. 4 is the torque ripple diagram that adopts the method provided by the present invention under the condition that the tertiary flux linkage does not change;

Fig. 5 is the torque ripple diagram that the method provided by the present invention is not adopted and the three-time flux linkage of the motor becomes 3 times the rated value (Ψ' _3f =3Ψ _3f );

FIG. 6 is a torque ripple diagram when the method provided by the present invention is adopted and the tertiary flux linkage of the motor becomes three times the rated value (Ψ' _3f =3Ψ _3f ).

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

A torque ripple suppression method for an open-winding permanent magnet synchronous motor provided by the present invention, as shown in Figure 1-2, specifically includes the following steps:

Step 1: Collect the three-phase stator current, motor speed, and rotor position angle of the open-winding permanent magnet synchronous motor at the current moment in real time, and convert each parameter into the form in the quadrature-axis d-q coordinate system;

Step 2: Establish a mathematical model for the permanent magnet synchronous motor in the d-q coordinate system, and use the deadbeat current predictive control model to predict the quadrature axis and the straight axis at the next moment in combination with the current moment parameters collected in step 1. and use the extended observer to perform model-free control in the zero-sequence loop of the model to predict the zero-sequence current and zero-sequence back EMF at the next moment;

Step 3: Using the zero-sequence current and zero-sequence back EMF predicted in step 2, calculate the required reverse injection value of quadrature current;

Step 4: Based on the calculation results in Steps 2 and 3, output the required voltage after torque ripple suppression, and use SVPWM for modulation.

In the existing schemes using the zero-voltage vector redistribution strategy for torque ripple suppression, they are discretized according to the mathematical model of the open-winding permanent magnet synchronous motor in the d-q coordinate system, while ignoring the third harmonic The high-order harmonics occupying a very small part can be predicted according to the measured motor information at time k at the time of (k+1) d, q axis and zero sequence current:

where U _d , U _q , and U ₀ are the direct axis, quadrature axis and zero-sequence voltage of the motor in the _dq coordinate system, respectively; id , i _q , and i ₀ are the direct axis, quadrature axis, and zero-sequence current, respectively; Ψ _f , Ψ _3f is the permanent magnet flux linkage and tertiary flux linkage of the motor rotor, respectively; R _s is the stator resistance; L _s and L ₀ are the d-axis, q-axis inductance and zero-sequence inductance, respectively; ω _r is the electrical angular velocity of the rotor, and T _k is a control cycle.

In the same way, the current at time (k+2) can be predicted according to the current at time (k+1), and it is assumed that the motor reference current at time k is reached at time (k+2), that is,

_id (k+2)= _id ^ref

i _q (k+2)=i _q ^ref

i ₀ (k+2)=i ₀ ^ref

Thus, the voltage required by the motor at (k+1) time can be obtained:

In the traditional deadbeat control, U _d , U _q , and U ₀ can be obtained by calculating the on-time of the inverter switch by the SVPWM modulation technique of zero vector redistribution, and controlling the on-off of the switch.

For the surface-mounted open-winding permanent magnet synchronous motor, the torque consists of two parts: the torque generated by the q-axis current and the torque generated by the zero-sequence current. In order to effectively suppress the torque generated by the zero-sequence current, assuming that the required reverse injection reference current value of the q-axis is i' _q , then

To make i' _q offset the torque ripple generated by the zero sequence current, namely:

Available

Among them, the third harmonic is taken as the main component of e0, namely

e ₀ =-3w _r ψ _3f sin(3θ)

It can be seen that the value of e ₀ is affected by the cubic flux linkage Ψ _3f .

However, the method provided by the present invention can obviously overcome the adverse effect of the three-time flux linkage on the inhibition effect. For example, in some examples of the present invention, the torque diagrams when the torque ripple suppression method is not applied and the third flux linkage does not change are compared, as shown in FIG. 3 and FIG. 4 . Under the condition that the tertiary flux linkage does not change, the torque ripple is very small, and the torque ripple generated by the zero-sequence current is effectively suppressed. However, when the tertiary flux linkage changes (the actual value of the tertiary flux linkage becomes three times the rated value, that is, Ψ' _3f = 3Ψ _3f ), we can clearly see that after adopting the method of this scheme (Fig. 6), The torque ripple is significantly reduced compared to the method without this scheme (Fig. 5). This shows that the method proposed in this scheme can still effectively suppress the torque ripple generated by the zero-sequence current when the three-time flux linkage changes. This is of great significance for improving the working stability of the motor and improving the working efficiency of the motor.

It should be understood that the size of the sequence numbers of the steps in the embodiments of the present invention does not imply the sequence of execution, and the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention .

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (4)

1. a torque ripple suppression method of an open-winding permanent magnet synchronous motor, is characterized in that: specifically comprises the following steps: Step 1: Collect the three-phase stator current, motor speed, and rotor position angle of the open-winding permanent magnet synchronous motor at the current moment in real time, and convert each parameter into the form in the quadrature-axis d-q coordinate system; In step 2, a mathematical model is established for the permanent magnet synchronous motor in the d-q coordinate system, combined with the current moment parameters collected in step 1, a deadbeat current predictive control model is adopted, and the intersection of the next moment is predicted based on the following formula: Shaft, direct shaft current:

In the _formula , k represents the current moment, k+1 is the next moment, id and i _q are the direct-axis and quadrature-axis currents, respectively,

are the predicted values of the quadrature-axis and direct-axis currents at the next moment, respectively, _wr is the electrical angular _velocity of the rotor, _Tk is a control period, Rs is the stator resistance, Ld _{=Lq = Ls} , _Ld , _Lq are the d-axis and q-axis inductances, respectively, U _d and U _q are the direct-axis and quadrature-axis voltages of the motor in the dq coordinate system, respectively, and Ψ _f is the permanent magnet flux linkage of the motor rotor; And in the zero-sequence loop of the model, the expansion observer is used to perform model-free control, and the zero-sequence current and zero-sequence back EMF at the next moment are predicted, including: The dilation observer is based on the following relation:

Among them, α is a parameter selected according to the motor controller, F≈e ₀ ; the initial value of e ₀ is set to 0, and U ₀ is the zero-sequence voltage in the dq coordinate system; the zero-sequence current and zero-sequence current at the next moment are predicted based on the following formulas Back EMF:

Among them, er ₀ (k) represents the predicted value of zero-sequence current at time k

The error from the actual value of the zero sequence current i ₀ (k),

that is

is the predicted value of the zero-sequence back-EMF, and β ₁ and β ₂ are the parameters of the extended observer; Step 3: Using the zero-sequence current and zero-sequence back EMF predicted in step 2, calculate the required reverse injection value of quadrature current; Step 4: Based on the calculation results in Steps 2 and 3, output the required voltage after the torque ripple is suppressed, and perform SVPWM modulation. 2. method as claimed in claim 1 is characterized in that: in described step 2, under described d-q coordinate system, the establishment of mathematical model to permanent magnet synchronous motor is specifically:

In the formula, U _d , U _q , and U ₀ are the direct axis, quadrature axis and zero-sequence voltage of the motor in the _dq coordinate system, respectively; id , i _q , and i ₀ are the direct axis, quadrature axis, and zero-sequence current, respectively; Ψ _f is Motor rotor permanent magnet flux linkage; R _s is stator resistance; L _d , L _q , L ₀ are d-axis, q-axis and zero-sequence inductance respectively; _wr is the electrical angular velocity of the rotor, e ₀ is zero-sequence back EMF, t is time; the model is based on the relationship of L _d =L _q =L _s in the surface mount open-winding permanent magnet synchronous motor; the above model is discretized. 3. The method according to claim 2, wherein: the quadrature current reverse injection value i' _q calculated in the step 3 is:

Substitute the zero-sequence current and the zero-sequence back EMF predicted in step 2 to obtain the reverse injection value of the quadrature-axis current. 4. The method of claim 3, wherein the required voltage after the output torque ripple is suppressed in the step 4 is specifically:

Among them, i _d ^ref (k), i _q ^ref (k), i ₀ ^ref (k) are the actual reference currents at time k, respectively.

Images